Axial-flow compressor, turbine, and the like



J 1 1947 A. A. GRIFFITH 2,414,410

AXIAL-FLQW COMPRESSOR, TURBINE, AND THE LIKE Filed Oct. 7, 1943 2 Sheets-Sheet 1 I arrows 5) Jan. 14, 1947. A. A. GRIFFITH ,414,410

AXIAL-FLOW COMPRESSOR, TURBINE, AND THE LIKE Filed Oct. 7, 1943 2 Sheets-Sheet 2 Q @AWZ deem/MW Patented Jan. 14, 1947 orrics AXIAL-FLOW COMPRESSOR, TURBINE, AND THE LIKE Alan Arnold Griflith, Derby,

England, assignor to Rolls-Royce Limited, Derby, England, a British company Application October 7, 1943, Serial No. 505,393

In Great Britain June 23, 1941 6 Claims.

1 This application corresponds to the application of Alan Arnold Griffith, Serial No. 7,898/41,

which was filed in Great Britain on June 23, 1941.

This invention concerns turbines, compressors and the like of the axial-flow type in which the rotor is made in two sections of different diameters, spaced apart axially to accommodate between them a support for the rotor-shaft, and it has for its object to provide a convenient construction of ducting to connect the two annular rotor-blade-spaces.

The invention is applicable to turbines or compressors, and in particular to power-units of the type described in the specification of my British patent application No, 4,699/41 which comprises an air-compressor and an internal-combustion turbine arranged in a single structure, with the compressor-blades carried on the same rotor elements as the turbine-blades. In that particular construction the rotor is constituted byseparate disc-like elements,,each carrying a set of turbineblades and a set of compressor-blades and mounted to rotate on a central fixed shaft, and it is desirable to provide a support for this shaft between two sets of rotor elements, such support being effected by radial arms extending from the shaft to the outer casing of the unit. The inletend of the compressor, which is also the outletend of the turbine, is of larger diameter than the other end, and it is necessary to convey the compressed air and the expanding gases of the turbine across the space between the two sets of rotor-elements.

According to this invention, there is provided in a turbine, compressor or the like, of the kind above described, a construction of ducting comprising a substantially conical assemblage of separately formed ducts arranged side-by-side circumferentially to provide an annular passage registering at each end with the rotor-bladespaces, said separate ducts being so formed as to accommodate betweenthem the supports for the rotor-shaft.

Preferably, the ducts in axial section are given a double reverse curvature or ogee formation to provide an easy path of flow for the gases concerned, from one set of rotor-blades to the other set.

, trio with the shaft l0.

iii

space between them for the purposes of heat-m sulation. c

According to yet another feature of this invention, each separate duct is divided transversely of its length into two parts with one part telescoped in the other, to facilitate the, assembly.

A construction of ducting in accordance with the present inventionfor use in a combined turbine and compressor will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a half-section through the ducting in a plane radial to the axis of the turbine and compressor rotors;

Figure 2 is a quarter-elevation of the ducting as seen from the left in Figure 1 with a part broken away to show the construction;

Figure 3 is an isometric projection of two of the ducts;

Figure 4 is an isometric of a single duct, and

Figure 5 shows a power unit embodying the inprojection of two parts vention with the upper half in section in a diametrical plane.

The construction of ducting illustrated in Figures 1 to 4 is designed for use in the power unit shown in Figure 5, The unit comprises a stationary shaft to (Figure 5) and a set of rotor discs 40 are mounted to rotate on the right hand portion of this shaft. ,Each rotor disc has an outer ring of turbine blades 4| and an inner ring of compressor blades 42, both rings being concen- A similar set ofrotor discs i3 rotate on the left hand portion of the shaft l0, and each of these rotor discs is of smaller diameter than those in has inner compressor blades 44 and outer turbine blades 55. Air enters at 46 and flows from right to left in Figure 5 and ducting 41 conveys the partly compressed air from the larger rotor discs ll! to thesmaller rotor discs 42. After the air has been compressed, it passes through a combustion chamber 48 in which fuel is burnt in it by a burner 69 and the products of combustion expand through the turbine blades 45 and M, flowing from left to right in Figure 5, to'

an outlet 50. The ducting shown also serves to convey the expanding gases from the smaller rotor discs 43 to the larger rotor discs 40.

The shaft i0 is supported by a bearing 5| carried by struts 52 from the casing 53 of the power unit.

The shaft III is also supported between the two sets of rotor discs by a bearing H (see also Fig-' ure 1) which is carried by a number of radial the first set and hand set of smaller rotor arms |2 which are integral with a cylindrical support IS. The support I3 is secured in ani suitablemanner to the casing 53 of the power unit.

The ducting 41 comprises three annular partitions ll, l and I6, Figures 1 and 2, to provide two passages I1 and I8 which are shaped as shown ,so that their right-hand ends register with the turbine and compressor blades on the right-hand set of rotor discs while the left-handends of the passages are nearer the shaft l0 so that they will register with the blades on the leftdiscs; each passage is thusroughly conical in shape. It'will be seen from Figure 1, that the ends of both passages are parallel to the shaft I] while their intermediate portions are reversely curved in a radial plane to avoid abrupt change in direction. Each of these passages is intersected by the arms l2 and a separate duct is provided in each of them between each pair of the arms so that each passage will contain an approximately conical assemblage of ducts.

Each duct in the passage I1 is formed of steel sheet in two parts 20 and 2| and the inner end of the part 20 is shaped to form a socket 22 intowhich the inner end 23 of the part 2| fits. Each part 20 and 2| is curved in longitudinal cross section as shown in Figures 1 and 4 and are assembled with their curvatures reversed so that the assembled duct has reversed curvature or ogee formation conforming to that of the passage H. The parts 20 and 2| are assembled by passing them through opposite ends of the passage H and entering the inner end 23 of, the part 2| into the socket 22 on the part 20. As shown in Figures 2 and 3, the parts 20 and 2| are curved in transverse cross-section to conform to the shape of the passage I1 and their widths at their outer ends are such that the ends of their side walls 24 and 25 abut, as shown in Figure 3, when the parts are assembled in the passage H to form the complete series of ducts. The openings at each end of the ducts thus occupy the whole of the circumferential length of the passage N. This has the result that the width of the outer end of the part 20 is greater than that of the outer end of the part 2| since the outer ends of the parts 2|! are further from the axis oi the assemblage and must collectively occupy a greater circumferential length. In order that the crosssectional area of each duct may be constant, the depth of each part of each duct varies along its length in accordance with its varying width and is a minimum at its right-hand and wider end. Each part of each duct decreases in width towards its inner end as shown in Figures 2 and 3 so that each duct is waisted to provide a space 36, when the ducts are assembled, between adjacent ducts through which one of the arms l2 passes with substantial clearance. As shown in Figure 1, the depth of. each duct is substantially less than that of the passage l1 and each part 20 and 2| is provided with flanges 26 to close the ends of the passage l1. 7

Each duct is thus surrounded by an air space which provides heat insulation around it. The two-part construction of each duct allows of its being assembled in the passage I1 and, after assembly, each duct is secured in position by securing its flanges 26 to the edges 01 the partitions l4 and I5. It should also .be noted that the risk of leakage of the hot gases through the joint between the two parts of each duct is minimised 4 by forming the socket 22 on the part 20 so that it faces the oncominglgases.

A similar assemblage of ducts, each formed in two parts 30 and 3|, is provided in the passage l8 and need not be described in detail. It should be mentioned that the socket 32 in each of these ducts is formed in the-part 3| so as to face the flow of partly compressed air which is in the opposite direction to that of the expanding gases. It will be seen that the hot gases passing through the ducts 202| are heat-insulated from the structure |2--|6 by the air space around those l ducts and are additionally insulated from the air being compressed as it passes through the ducts 30-3! by the air. space between those ducts and the walls of the passage l8, thereby preventing loss of efflciencyin either the turbine or the compressor. The assembly shown in Figures 1 and 2 is mounted between two members carrying guide vanes to direct the hot gases and partly compressed air flowing from the assembly to the next set of turbine and compressor blades respectively and suitable packing may be provided between the assembly and these members. I

I claim:

1. In axial-flow turbines, compressors and the like, the combination of a rotor having two parts of differing diameters spaced apart axially, sup-' porting means engaging the rotor-shaft between said two portions, a substantially conical assemblage of separately'formed ducts arranged side by side and providing an annular passage registering at each end with the rotor-blade spaces, said ducts being so formed as to accommodate betwen them the said supports for the rotor-shaft. 2. In axial-flow turbines, compressors and the like, the combination of a casing, a rotor-shaft mounted therein, blade-carrying elements on said rotor of two different diameters spaced apart axially, means supporting said rotor-shaft between said .two elements, a plurality of separately formed ducts arranged side by side to provide an annular passage registering at each end with the rotor-blade spaces, said ducts in axial section each having a double reversed curvature, and being'so formed as to accommodate between them the said supports for the rotor-shaft.

3. In axial-flow turbines, compressors and the like, the combination of a casing, a shaft within said casing, two blade-carrying rotor elements of different diameters spaced apart axially on said shaft, a substantially conical assemblage of separately formed ducts arranged side by sideproviding an annular passage registering at each end with the rul -blade spaces, each of said ducts being divided transversely of its length into two parts telescoped one within the other to facilitate assembly.

4. In axial-flow turbines, compressors and the like, the combination of a casing, a shaft within said casing, rotor-elements or two different diameters spaced apart axially on said shaft, a substantially conical assemblage of separately formed ducts arranged side by side providing an annular passage registering at each end with the rotor-blade spaces, said ducts being located in ments, one set allocated to the compressor and the other set allocated to the turbine, means providing communication between two sets of compressor-blades of diflering diameter and also between two sets of turbine blades of diflering diameter comprising separately formed ducts arranged side by side in a substantially conical assemblage, each of said ducts being reversely curved along its length and divided into two parts transversely of its length, said parts being telescoped one within the other, supporting means for said rotorshaft extending between said ducts, and a casins surrounding said rotor-elements spaced away from said ducts to provide a heat-insulating air space.

6. An axial-flow combined compressor and turbine according to claim 5, wherein the ducts for the compressor blades are spaced apart from the ducts for the turbine blades to provide a heatinsulating air space between them.

ALAN ARNOLD GRIFFI'I'H. 

